filter_by_comparison
void filter_by_comparison(struct range_list **rl, int comparison, struct range_list *right);
filter_by_comparison(&rl, comparison, orig_rl);
filter_by_comparison(&rl, comparison, orig_rl);
filter_by_comparison(&var_rl, comparison, ret_range);
filter_by_comparison(&ret_range, flip_comparison(comparison), var_rl);
filter_by_comparison(&var_rl, negate_comparison(comparison), ret_range);
filter_by_comparison(&ret_range, flip_comparison(negate_comparison(comparison)), var_rl);
filter_by_comparison(&casted_start, comparison, right_orig);